Back to Search
Start Over
Ca isotopes record rapid crystal growth in volcanic and subvolcanic systems.
- Source :
-
Proceedings of the National Academy of Sciences of the United States of America . Oct2019, Vol. 116 Issue 41, p20315-20321. 7p. - Publication Year :
- 2019
-
Abstract
- Kinetic calcium isotope effects can be used as growth-rate proxies for volcanic and subvolcanic minerals. Here, we analyze Ca isotopic compositions in experimental and natural samples and confirm that large kinetic effects (>2?) can occur during magmatic plagioclase crystallization. Experiments confirm theoretical predictions that disequilibrium isotope effects depend mainly on the rates for crystal growth relative to liquid phase Ca diffusivity (R/D). Plagioclase phenocrysts from the 1915 Mount Lassen rhyodacite eruption, the ~650-y-old Deadman Creek Dome eruption, and several mafic subvolcanic orbicules and plagioclase comb layers from Northern California have disequilibrium Ca isotopic compositions that suggest rapid crystal growth rates (>1 cm/y to 15 cm/y). The Ca isotope results, combined with complementary crystal-size distribution analyses, suggest that magmatic rejuvenation (and eruption) events, as reflected in crystal growth times, can be as short as ~10-3 y. Although mafic systems are predicted to have shorter magmatic rejuvenation periods, we find similarly short timescales in both mafic and silicic systems. These results are consistent with a growing body of evidence suggesting that dominantly crystalline volcanic magma reservoirs can be rapidly reactivated by the injection of fresh magma prior to eruption. By focusing on a commonmineral such as plagioclase, this approach can be applied across all major magmatic compositions, suggesting that Ca isotopes can be used as a tool for investigating the dynamics and timing of volcanic eruptions. [ABSTRACT FROM AUTHOR]
- Subjects :
- *CRYSTAL growth
*KINETIC isotope effects
*ISOTOPES
*VOLCANIC eruptions
*PLAGIOCLASE
Subjects
Details
- Language :
- English
- ISSN :
- 00278424
- Volume :
- 116
- Issue :
- 41
- Database :
- Academic Search Index
- Journal :
- Proceedings of the National Academy of Sciences of the United States of America
- Publication Type :
- Academic Journal
- Accession number :
- 139095305
- Full Text :
- https://doi.org/10.1073/pnas.1908921116